This neutron star drilled through its partner, an extremely rare event

Astronomers have discovered a remarkable pair of stars that provides insights into how stars interact and transform each other. The system consists of a rapidly spinning neutron star and a helium star that has lost its outer layers. This duo is so rare that it offers a unique glimpse into the wild life cycles of stars.

The main character in this story is PSR J1928+1815, a neutron star detected by China's FAST radio telescope. This pulsar rotates at an astonishing speed, completing nearly 100 rotations per second. The neutron star orbits a helium star every 3.6 hours, which has been significantly stripped of its material.

Scientists believe the system evolved when the original star expanded and engulfed the neutron star, which then burrowed through its partner, ejecting hydrogen-rich layers and leaving behind a compact helium star. This process is analogous to what our Sun will experience in about five billion years when it becomes a red giant.

Despite efforts, the helium star remains elusive due to distance and interstellar dust. The pulsar itself is obscured about 17% of the time by the helium star. Estimates suggest only 16 to 84 such systems exist in the Milky Way, making this a cosmic needle in a haystack.

In the future, the helium star may expand again and transfer material to the neutron star, eventually forming a rapidly spinning pulsar with a white dwarf companion. However, this will unfold over millions of years.